Detailed Guide to Prevention and Control of Cymbidium Mosaic Virus and Fertilization Methods for Orchids

Symptoms

Initially faded spots appear, then spread along the leaf veins; adjacent lesions merge to form elongated faded lesions, presenting as mosaic disease. After the leaves mature, the faded streaks become necrotic.

Pathogen

Cymbidium mosaic virus (CyMV), which occurs worldwide. The virus particles are about 480 nm long and about 13 nm wide, and the virus is easily transmitted mechanically through sap. This virus naturally infects as many as 38 genera of orchids, making it the virus with the widest host range among orchids.

Transmission routes: during division and transplanting, the virus can be carried on the fingers and tools such as scissors used to handle infected plants, and can be transmitted to healthy plants they contact. The roots of diseased plants are easily damaged, and the virus can flow out from the bottom of the pot during watering, making it infectious.

Prevention and Control Methods

Prevention and control of orchid viruses should focus on prevention.

1. Once diseased plants are found, destroy them immediately. If they are rare varieties, they should also be isolated and given enhanced management.

2. When propagating by division, fingers and tools should be washed with soapy water. Do not use the same bucket of water to wash many plants; instead, wash them one by one under running water. Potting soil, moss, pots, and other items should also be disinfected beforehand before use.

Currently, the internationally recognized better disinfectant solutions include: (1) 2% formalin and 2% sodium hydroxide aqueous solution (cannot be used once it turns green); (2) 164 grams of anhydrous trisodium phosphate (NaPO4) or 377 grams of trisodium phosphate containing water of crystallization, added to 1000 ml of water, can be used to disinfect tools, cultivation environments, and so on.

3. When using diseased plants as female parents for pollination, fully mature seeds should be used for sowing.

4. Plants outside the orchid family, such as those in the Solanaceae, Fabaceae, and Chenopodiaceae, may also carry the virus and become infected, so attention should be paid to this in prevention and control.

Diagnostic Methods

(1) The faded spots or elongated faded spots produced on leaves appear mosaic-like, then necrose into dark brown lesions.

(2) Under electron microscopy, the virus particles are about 480 nm long, and it can basically be diagnosed as CyMV.

(3) Diagnosis is carried out by testing with CyMV antiserum.

(4) Diagnosis can be made by the inoculation reaction on indicator plants such as Chenopodium amaranticolor, New Zealand spinach, Datura stramonium, and Cassia occidentalis.